U.S. Pat. No. 4,763,667 (Manzo) issued Aug. 16, 1988, describes a tissue-penetrating catheter device useful in performing amniocentesis, having an inner catheter with a tissue-penetrating device, e.g., a needle, joined to the distal end of the inner catheter. The inner catheter is contained in an outer catheter and there is an element situated between the proximal ends of the inner and outer catheters which permits adjustment of the distance the tissue-penetrating device will extend.
U.S. Pat. No. 4,308,875 (Young) issued Jan. 5, 1982, describes an amniocentesis needle comprising a blunt-end needle and a stylet in the lumen of the needle. The stylet projects a short distance from the end of the needle on insertion and as soon as the needle is inserted the stylet is withdrawn from the needle.
U.S. Pat. No. 2,389,355 (Goland) issued Nov. 20, 1945, describes a needle for injecting fluids comprising a double cannula (inner and outer) with a rod in the inner cannula. The rod has no tissue piercing function, but rather serves as a means to prevent fluid from entering the cannula chamber.
U.S. Pat. No. 1,248,492 (Hill) issued Dec. 4, 1917, describes a cannula for withdrawing fluid comprising of a cannula/stylet combination wherein the cannula is slidably adjustable over the stylet.
U.S. Pat. No. 1,147,488 (Kells) issued Jul. 20, 1915, describes a needle having a sheath which surrounds the tissue at the point of puncture for the purpose of collecting any tissue fluids that may leak out around the puncture.
U.S. Pat. No. 3,628,524 (Jamshidi) issued Dec. 21, 1971, describes a biopsy needle having a stylet of substantially the same length situated inside the needle. The purpose of the stylet is to push the biopsy sample from the needle.